Thank you for the opportunity to answer your question. I am sending this answer to you only a few minutes after you submitted your question.
It's not possible to review documents, in whole or in part, in this forum. For that reason, it's not possible for me to review your email. However, I can explain how the law works.
A one-way email doesn't bind anyone to anything but a mutual agreement can, and an agreement can be reached through email. In other words, if a seller sends a buyer a receipt for partial payment, that could provide evidence in a legal action arising from the sale. However, it would not constitute a contract
because the other party has not indicated agreement to anything. On the other hand, a contract could be created through email if an individual sent an email stating "I will sell you the item in exchange for $1,000 and you will be able to pick it up on July 1, 2012" and if the other party responded with "I accept."
Payment can provide evidence that an oral agreement was reached, as can the provision of a receipt. If two people enter into an oral agreement, that could bind both you and the other party. For example, if you've already agreed that the buyer will pay a certain amount but that the car will not be delivered until a certain date, the buyer would be bound by that agreement and wouldn't generally be entitled to a refund. However, if the buyer sued you, you'd need to be able to show that there was an agreement that the vehicle would be delivered at a later date and not immediately upon receiving payment.